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Jan. 7, 1964 N. A. DE GIER DISC-SHAPED ELECTRIC IMPEDANCE ELEMENT I Filed June 15, 1961 Has NICO A. DE GIER.

AGENT United States Patent 0 M 3,117,297 DlSC-fiHAlPED ELEQTREQ EWEDANUE ELEl'vlENT Nico Arie de Glen, Einmaslngel, Eindhoven, Netherlands, assignor to North American Philips (Iompany, line, New York, N.Y., a corporation of Delaware Filed June 13, m l, gen, No. 116,5523 Claims priority, application Netherlands lniy 22, rate 8 Claims. (Cl. 3533-19) This invention relates to disc-shaped electric impedance elements or components with a layer or member of insulating or semi-conductive material, provided with at least two electrodes each extending to a different part of the edge of the disc.

Small ceramic capacitors are known comprising a discshaped dielectric, in which the current-supply wires for the electrodes provided on each side of the disc-shaped dielectric are soldered in position at the centre thereof. The current-supply wires may be provided by clamping the ceramic disc between the ends of a wire bent into the shape of a hairpin and, subsequently, dipping the disc in a bath of solder, followed by cutting through the hairpin-shaped wire usually in the vicinity of the bend.

In a photo-conductive resistor comprising a disc of pressed and sintered photo-conductive cadmium sulphide provided with two interlaced comb-shaped electrodes, the current-supply wires are sometimes formed by wires fixed transversely of the surface of the disc in a hardpaper carrier for the disc, the ends of the wires being connected to the electrodes with the aid of a conductive paste. Such a resistor may readily be placed in a suitable vessel of transparent material, for example of glass, whereafter the vessel is sealed with the aid of an insulating material, for example an ethoxylene cast resin, the current-supply wires extending through this seal. Like the aforementioned known structure of ceramic capacitors, such a photoconductive cell has the disadvantage that the total element is comparatively voluminous, which may cause ditliculty for a number of uses. The structure with the vessel has the further disadvantage that a satisfactory seal is not always ensured due to the different coefficients of expansion of the material of the vessel and of the sealing material.

An object of the invention is to provide an impedance element of the kind described in the preamble, more particularly a photo-conductive cell, having small dimensions in at least one direction which is satisfactorly protected against atmospheric influences.

According to the invention, at least two current-supply wires are provided on the edge of the disc and, following the circumference thereof, approach each other to bend at a short distance from each other and extend away from the edge of the disc, the portions of the current-supply wires engaging the circumference of the disc each being connected to an electrode with the aid of a conductive cement and the disc, together with these portions of the current-supply wires, being provided with an insulating layer enveloping the assembly. This structure affords the advantage that the impedance element including the protective envelope is very fiat.

In one advantageous embodiment of the invention, the current-supply wires which extend away from the disc in a more or less parallel direction are held in position at approximately their bends by means of an insulating ring surrounding them and embedded in the insulating envelope. The pull-off force of the current-supply wires is thus considerably increased. For the insulating material of the envelope use is preferably made of a celluloseacetate-butyrate lacquer. Such a lacquer has been found to be properly moisture-tight, to have a comparatively high softening point and, which is important more particularly Patented Jan. '7, H564 for photoconductive cells, to be substantially colourless and to discolour little, if any, in time.

In manufacting the component of the invention, a wire is bent into the form of a hairpin so that the limbs extending in parallel have bulges located at opposing areas in the plane of the hairpin and each matched to a portion of the circumference of the disc whereupon the disc is laid flat between the bulges of the hairpin so that each bulge resiliently engages along a peripheral portion of the disc with an electrode extending thereto and, subsequently, each bulge is conductively connected to an electrode with the aid of a conductive cement, Whereafter an insulating ring holding the limbs in a fixed position is slipped onto the hairpin up to near the edge of the disc, and the disc, the ring and the portions of the hairpin in contact with both of them are provided with an insulating envelope by immersion, whereupon the portion of the wire with the bend connecting the limbs is cut oil.

in order that the invention may be readily carried into effect, one embodiment thereof will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawing, in which:

FIGURE 1 shows a photo-conductive cell with currentsupply wires;

FIGURE 2 is a cross-sectional view, taken along the line ill-11 of FIGURE 1;

FIGURES 3, 4 and 5 show several phases of providing the current-supply wires on the photoconductive cell of FIGURES l and 2.

The photoconductive cell of FlGURE-S l and 2 comprises a circular plate 1 of cadmium sulphide, which has been pressed and sintered and one side of which is provided with two interlaced comb-shaped electrodes 3 and 4. The electrodes may extend to the edge of the disc l. A curved portion 6 of a first current-supply wire 5, which extends in the plane of the disc 1, engages that edge of the disc towards which the electrodes 3 are directed. The wire portion 6 is conductively connected to the electrode 3 with the aid of a conductive cement 7 which is, for example, a silver paste.

Similarly, a curved portion 9 of a second current-supply wire 8, which engages the opposite edge of the disc l, is conductively connected to the electrode 4 with the aid of a conductive cement iii.

The current-supply wires 5 and ii are surrounded by an insulating ring ill at the area where the wire portions 6 and 9 approach each other and merge into the portions of the current supply wires 5 and ti extending away from the plate It in a parallel direction. The disc 1, the engaging wire portions 6 and 9, the ring Ill and the portions of the Wires 5 and d surrounded by it are enveloped by a closed insulating layer 12. The envelope 1?; consists of a transparent lacquer or synthetic resin, for example a resin of the ethoxylene type. An envelope consisting of a cellulose-acetate-butyrate lacquer is very favourable and can be provided more readily than an ethoxylene resin layer.

As may be seen from FIGURES l and 2, the volume of the whole is maintained as small as possible owing to the particular manner in which the supply wires 5 and 8 are in contact with the photoconductive disc 1. More particularly the dimension in the direction transveres to the surface of the disc 1, that is the direction from which the radiation falls upon the photoconductive resistor, is little larger than the thickness of the plate Ll itself, while the supply wires do not extend over the photo-sensitive surface.

The manner in which the current-supply wires 5 and 3 are provided on the plate 1 is illustrated in FIGURES 3, 4 and 5. A Wire is bent into the form of a hairpin 39 (FIGURE 3), the two limbs 5 and 8 being provided with bulges 6 and 9 respectively at opposing areas and not too far from the bend 311 of the hairpin, which bulges are matched to opposing peripheral portions of the disc The hairpin is bent so that the distance indicated by 32 in FIGURE 3 is a litt e less than the diameter of the disc 1. Subsequently, while the hairpin 20 lies on a supporting surface, the limbs and 8 are extended away from each other (shown in broken lines in FIGURE 4), the disc 1 is laid between the bulges 6 and 9 and the limbs 5 and 8 are released so that the wire portions 6 and 9 resiliently clamp the disc 11 in position (shown in full lines in FIGURE 4). Now, silver pastes 7 and respectively are provided on the wire portions 6 and 9 respectively and the adjacent portions of the electrodes (FEG'URE 5). A little lacquer may be added to the silver paste for increasing the adhesion. It is then favourable to choose the la quer so that it does not dissolve in the solvent of the lac- 'quer envelope to be described hereinafter.

After drying of the silver pastes 7 and 10 respectively, an insulating ring 11 consisting, for example, of a piece of insulation sleeve of synthetic material is slipped onto the ends 5 and 8 of the hairpin, which extend closely in parallel, up to near the disc ll (FIGURES 4 and 5).

Subsequently, the element while being held at the ends of the hairpin 30 is dipped in a solution of a celluloseacetate-butyrate lacquer so far that the ring 11 is immersed. The element thus acquires a lacquer envelope. After this lacquer envelope has dried, the hairpin 3G is cut through at the side of the bend 31, for example along the line 5tl-5tl in FIGURE 5. Subsequently, the element is again dipped in the said liquid lacquer in order to strengthen the insulating envelope formed during the first immersion so as to obtain the lacquer layer 12 of FIG- URE 1 and also to provide the free ends of the wire portions 6 and 9, resulting from cutting off the bend 31, with an insulating layer. The element obtained with the described method is shown in FIGURES l and 2.

In the foregoing the invention has been explained with a description of a photoconductive cell and a method of providing current-supply wires on such a cell. It will be clear that the invention is not limited to a photoconductive cell but may be used in any case where the impedance element proper is formed by a disc-shaped body provided with electrodes each extending to a different part of the edge. Thus, the invention is also applicable to a ceramic capacitor with a disc-shaped dielectric, having an electrode on each side, and to an electro-luminescent cell in which an electro-luminescent layer provided on an insulating carrier plate is provided with electrodes extending to different peripheral portions of the carrier plate.

The use of an insulating ring within the insulating enveloped, embracing the parallel-directed supply wires, results in a pull-off force higher than would be the case in the absence of such a ring. However, instead of an in sulating ring holding the two wires together, it is also possible to use a drop of lacquer at the same area. In this case the pull-off force is usually a little less, unless a strong kind of lacquer is used for this drop.

What is claimed is:

1. An electrical component comprising a generally discshaped member having circumferential portions, said discshaped member including an active element and at least two spaced electrodes connected to the active element, at least two conductive leads, each of said leads having an dend portion engaging a circumferential portion of the discshaped member, means connecting the said end portion of each lead to one of the electrodes, and an insulating coating enveloping the disc-shaped member, electrodes, conductive lead end portions, and connecting means.

2. A component as set forth in claim 1 wherein the insulating coating is transparent.

3. A component as set forth in claim 2 wherein the coating is a cellulose-acetate-butyrate lacquer.

4. An electrical component comprising a generally flat disc-shaped member having circumferential portions, said disc-shaped member including an active element selected from the group consisting of insulators and semi-conductors and at least two electrodes each connected to a different region of the active element and extending to the vicinity of a different circumferential portion of the discshaped member, at least two conductive leads substantial portions of the ends of which extend generally parallel to one another, the other ends of the leads engaging opposed circumferential portions of the disc-shaped member, conductive adhesive means securing together and electrically connecting each electrode with an engaged end of a conductive lead, and an insulating layer completely enveloping the member, electrodes, adhesive means, and engaged ends of the conductive leads.

5. An electrical component comprising a generally flat disc-shaped member having circumferential portions, said disc-shaped member including an active element selected from the group consisting of insulators and semi-conductors and at least two electrodes each connected to a diiferent region of the active element and extending to the vicinity of a different circumferential portion of the disc shaped member, at least two conductive leads substantial portions of the ends of which extend generally parallel to one another and form a common plane with the discshaped member, the other ends of the leads engaging 0p posed circumferential portions of the disc-shaped member and having an arcuate shape, conductive adhesive means securing together and electrically connecting each electrode with an engaged end of a conductive lead, means scouring together the conductive leads intermediate their parallel ends and engaged ends, and an insulating layer completely enveloping the member, electrodes, adhesive means, engaged ends of the conductive leads, and the securing means.

6. A component as set forth in claim 5 wherein the securing means for the leads is an insulating ring.

7. A component as set forth in claim 5 wherein the discshaped member is constituted of pressed and sintered photoconductive material, and the two electrodes are interlaced comb-shaped members on the same surface of the member.

8. A component as set forth in claim 7 wherein the member is of cadmium sulphide.

References Cited in the tile of this patent UNITED STATES PATENTS 2,081,894 Meyer et al May 25, 1937 2,731,533 Magrath Jan. 17, 1956 2,958,932 Goerclie Nov. 8, 1960 2,960,757 Epstein Nov. 22, 1960 

1. AN ELECTRICAL COMPONENT COMPRISING A GENERALLY DISCSHAPED MEMBER HAVING CIRCUMFERENTIAL PORTIONS, SAID DISCSHAPED MEMBER INCLUDING AN ACTIVE ELEMENT AND AT LEAST TWO SPACED ELECTRODES CONNECTED TO THE ACTIVE ELEMENT, AT LEAST TWO CONDUCTIVE LEADS, EACH OF SAID LEADS HAVING AN END PORTION ENGAGING A CIRCUMFERENTIAL PORTION OF THE DISCSHAPED MEMBER, MEANS CONNECTING THE SAID END PORTION OF EACH LEAD TO ONE OF THE ELECTRODES, AND AN INSULATING COATING ENVELOPING THE DISC-SHAPED MEMBER, ELECTRODES, CONDUCTIVE LEAD END PORTIONS, AND CONNECTING MEANS. 